Table 2. Antibody subtypes and estimated titers by SPR.
| Subject | FVIII-C2 competition assay | Time since inhibitor diagnosis | IgG1+2+3+4 (RU)a/polyclonal IgG (RU) | % IgG1 | % IgG2 | % IgG3 | %IgG4 | Total anti-FVIII IgG (µg/ml) |
| Q-011 | day1 | 0.96 | 79% | 4% | −1% | 18% | 34.25 | |
| day4 | 0.96 | 71% | 9% | −1% | 22% | 27.43 | ||
| 4 wk | 1.2 | 78% | 5% | −1% | 18% | 22.49 | ||
| 6 wk (n = 3)b | 1.09(.30)c | 69%(4%) | 10%(1%) | −2%(1%) | 23%(2%) | 6.02(3.79) | ||
| 8 wk (n = 3) | 1.17(.74) | 72%(7%) | 10%(2%) | −1%(3%) | 19%(3%) | 1.36(0.95) | ||
| 22 wk (n = 2) | 0.97(.05) | 89%(7%) | 4%(2%) | −2%(2%) | 9%(4%) | 0.94(0.11) | ||
| 32 wk (n = 2) | 1.04(.03) | 83%(1%) | 2%(0%) | −1%(0%) | 15%(1%) | 1.58(0.35) | ||
| Q-012 | day1 (n = 4) | 1.02(.04) | 6%(1%) | 2%(4%) | −1%(0%) | 94%(5%) | 6.40(3.66) | |
| day7 | 1 | 6% | 5% | −1% | 90% | >23.50 | ||
| day9 (n = 3) | 0.99(.06) | 6%(0%) | 5%(1%) | 1%(1%) | 90%(0%) | 8.90(4.14) | ||
| day13 (n = 2) | 0.99(.11) | 7%(0%) | 4%(0%) | 0%(1%) | 89%(1%) | 6.72(1.97) | ||
| 26 wk | NDd | ND | ND | ND | ND | <0.2 | ||
| 34 wk | ND | ND | ND | ND | ND | <0.2 | ||
| 42 wk | ND | ND | ND | ND | ND | <0.2 | ||
| 17A | (−) FVIII-C2 | 1 wk | 1 | 101% | 0% | −1% | −1% | 31.39 |
| (+) FVIII-C2 | 0.7 | 102% | 0% | −1% | −1% | 9.11 | ||
| (−) FVIII-C2 | 3 wk | 1.05 | 101% | 1% | −1% | 0% | 23.54 | |
| (+) FVIII-C2 | 0.74 | 104% | −1% | −3% | −1% | 1.42 | ||
| (−) FVIII-C2 | 51 wk | 1.04(.01) | 99%(0%) | 1%(0%) | (1%)(0%) | 1%(0%) | 5.49(0.09) | |
| (+) FVIII-C2 | ND | ND | ND | ND | ND | <0.2 | ||
| (−) FVIII-C2 | 5 yrs | 1.11(.02) | 95%(2%) | 0%(1%) | −1%(0%) | 5%(1%) | 3.11(0.62) | |
| (+) FVIII-C2 | ND | ND | ND | ND | ND | <0.2 | ||
| L-006 | 1 wk | 0.87 | 92% | 4% | 4% | 0% | 11.85 | |
| 5 wk (n = 2) | 0.98(.01) | 91%(2%) | 2%(4%) | 4%(0%) | 3%(2%) | 13.13(1.46) | ||
| 9 wk | 0.98 | 85% | 6% | 2% | 7% | 11.97 | ||
| 21 wk | ND | ND | ND | ND | ND | <1.09 | ||
| 35 wk | ND | ND | ND | ND | ND | <0.99 |
a
The ratios indicate the agreement between the summed SPR signals from the binding of secondary detection antibodies specific for IgG1, IgG2, IgG3 and IgG4 (numerator) to the initial SPR signal generated by the anti-FVIII antibodies in plasma that bound to the immobilized FVIII (denominator).
b
Multiple measurements (n) were made when sufficient plasma was available.
c
Standard deviations are reported for these experiments in parentheses.
d
ND = Not Determined because the low total IgG titer made estimates of ratios and %Ig subtypes unreliable.